Supplemental Oil and Gas Information - Proved Reserves Quantities (Details)	12 Months Ended
	Jun. 30, 2012 MBbls		Jun. 30, 2011 MBbls		Jun. 30, 2010 MBbls
Oil (in Mbbls)
Proved Developed and Undeveloped Reserves [Abstract]
Proved Reserves, Beginning Balance	9,190,000		9,478,000		996,000
Extensions and discoveries	186,400		6,000		6,963,000
Revision of previous estimates	(1,643,800)		(340,000)		(768,000)
Purchase of minerals in place	1,246,800		178,000		2,631,000
Sales of minerals in place					(205,000)
Production	(74,200)		(132,000)		(139,000)
Proved Reserves, Ending Balance	8,905,200		9,190,000		9,478,000
Proved Developed Reserves (Volume)	1,646,700		2,249,000		2,515,000
Proved Undeveloped Reserves (Volume)	7,258,400		6,941,000		6,963,000
Gas (in MMcf)
Proved Developed and Undeveloped Reserves [Abstract]
Proved Reserves, Beginning Balance	400		1,500		3,300
Extensions and discoveries	0		0		0
Revision of previous estimates	6,000		(200)		1,600
Purchase of minerals in place	5,500		0		0
Sales of minerals in place					0
Production	(400)		(900)		(3,400)
Proved Reserves, Ending Balance	11,500		400		1,500
Proved Developed Reserves (Volume)	11,500		400		1,500
Proved Undeveloped Reserves (Volume)	0		0		0
United States | Oil (in Mbbls)
Proved Developed and Undeveloped Reserves [Abstract]
Proved Reserves, Beginning Balance	9,190,000		9,478,000		0
Extensions and discoveries	186,400		6,000		6,963,000
Revision of previous estimates	(1,643,800)		(404,000)		(74,000)
Purchase of minerals in place	1,246,800		178,000		2,631,000
Sales of minerals in place					0
Production	(74,200)		(68,000)		(42,000)
Proved Reserves, Ending Balance	8,905,200		9,190,000		9,478,000
Proved Developed Reserves (Volume)	1,646,700		2,249,000		2,515,000
Proved Undeveloped Reserves (Volume)	7,258,400		6,941,000		6,963,000
United States | Gas (in MMcf)
Proved Developed and Undeveloped Reserves [Abstract]
Proved Reserves, Beginning Balance	0		0		0
Extensions and discoveries	0		0		0
Revision of previous estimates	0		0		0
Purchase of minerals in place	0		0		0
Sales of minerals in place					0
Production	0		0		0
Proved Reserves, Ending Balance	0		0		0
Proved Developed Reserves (Volume)	0		0		0
Proved Undeveloped Reserves (Volume)	0		0		0
Australia | Oil (in Mbbls)
Proved Developed and Undeveloped Reserves [Abstract]
Proved Reserves, Beginning Balance	0	[1]	0	[1]	996,000	[1]
Extensions and discoveries	0	[1]	0	[1]	0	[1]
Revision of previous estimates	0	[1]	64,000	[1]	(694,000)	[1]
Purchase of minerals in place	0	[1]	0	[1]	0	[1]
Sales of minerals in place					(205,000)	[1]
Production	0	[1]	(64,000)	[1]	(97,000)	[1]
Proved Reserves, Ending Balance	0	[1]	0	[1]	0	[1]
Proved Developed Reserves (Volume)	0	[1]	0	[1]	0	[1]
Proved Undeveloped Reserves (Volume)	0	[1]	0	[1]	0	[1]
Australia | Gas (in MMcf)
Proved Developed and Undeveloped Reserves [Abstract]
Proved Reserves, Beginning Balance	400	[1]	1,500	[1]	3,300	[1]
Extensions and discoveries	0	[1]	0	[1]	0	[1]
Revision of previous estimates	6,000	[1]	(200)	[1]	1,600	[1]
Purchase of minerals in place	5,500	[1]	0	[1]	0	[1]
Sales of minerals in place					0	[1]
Production	(400)	[1]	(900)	[1]	(3,400)	[1]
Proved Reserves, Ending Balance	11,500	[1]	400	[1]	1,500	[1]
Proved Developed Reserves (Volume)	11,500	[1]	400	[1]	1,500	[1]
Proved Undeveloped Reserves (Volume)	0	[1]	0	[1]	0	[1]

[1] The amount of proved reserves applicable to Australia gas reflects the amount of gas committed to specific contracts and is net of royalties.